Screen printing apparatus has been known for very many years. In recent years a wide variety of screen printing machines has been developed for reducing the high labour content of screen printing associated with so-called hand-bench operation. Screen printing using a hand-bench is also a highly skilled operation and for long production runs this is also uneconomic.
Screen printing apparatus for printing materials is described inter alia in British patent specification Nos. 1,200,481; 821,090; 395,900; 316,467 and 180,869, German Auslegeschrift No. 1038067 and British patent specification Nos. 1,367,441 and 1,549,748.
Screen printing has classically been used for printing jobs where solid colours were required such as for posters and placards and it has found particular application in fields where relatively low print definition is required. It requires considerable skill to print more than one image satisfactorily in register by silk screen printing due to the inherent deformability of the silk screen itself.
In recent years, however, screen printing has been adopted as the printing method of choice in the manufacture of dry transfer lettering and symbol sheets for use in the graphic arts and other fields. In this application it is of substantial importance that each of the letters on each sheet of dry transfer material be accurately printed with high edge definition and no distortion. Automatic screen printing machines designed or adapted to print such dry transfer lettering and symbol sheets up till now have fulfilled these requirements only to a limited degree.
It is an object of the present invention to provide a screen printing machine which overcomes certain of the disadvantages of the prior art. It is a further object of the invention to provide a screen printing machine which is particularly adapted for high quality screen printing such as is required, for example, in the manufacture of dry transfer lettering and symbol sheets.